Low-density Quantum Dots Research Articles

Generating visible single photons on demand with single InP quantum dots

We present photon correlation measurements performed on a device based on single InP quantum dots. The device consists of a 400 nm thick membrane containing a low density of quantum dots on a metal mirror. Measurements done under continuous excitation reveal a very pronounced antibunching dip while measurements done under pulsed excitation enable the generation of single photons on demand at the optimum wavelength for silicon-based single-photon detectors.

Wetting layer carrier dynamics in InAs/InP quantum dots

The electronic coupling between InAs/InP quantum dot (QD) array and its wetting layer (WL) is studied by continuous wave and time resolved photoluminescence. The carrier dynamics is explained by the existence of two regimes in the WL: at low QD density the carrier dynamics is dominated by the diffusion and at high density when the distance between QDs is comparable to the carrier mean free path in the WL the quantum capture into QDs dominates. From the identification of these two regimes the carrier mean free path in the WL is estimated to about 30 nm.

Carrier capture and relaxation in quantum dot structures with different dot densities

Carrier dynamics has been measured by time-resolved photoluminescence in self-assembled InGaAs/GaAs quantum dot structures with dot density of the order of 10 8 to 10 10 cm 2. The time of carrier transfer into a dot, which is in the region from 2 to 20 ps, has been found to decrease with increasing quantum dot density. The temperature and photoexcited carrier density dependencies of the carrier transfer times suggest that potential barriers at the barrier, wetting layer and quantum dot interfaces hinder carrier capture in low-density quantum dot structures.

Carrier dynamics in quantum dot structures with different interdot spacings

Photoexcited carrier dynamics have been examined by time-resolved photoluminescence in InGaAs/GaAs quantum dot structures with dot density ranging from 3.7×10 8 to 2.4×10 10 cm −2. The time of carrier transfer into a dot decreases with increasing dot density as well as with photoexcited carrier density and temperature. It is suggested that potential barriers at the barrier, wetting layer and quantum dot interfaces hinder the carrier capture in low-density quantum dot structures.

Finite Carrier Confinement and Biexcitonic Complexes in Self-Assembled Inas Quantum Dots

AbstractThe luminescence properties of a single lnAs self-assembled quantum dot (QD) are studied by confocal scanning optical microscopy at low temperature. The observation of single QDs has been accomplished by epitaxial growth of QDs samples with low QD density (less than one QD per μm2) required by the diffraction limited spatial resolution of the microscope. In thick QDs with large confinement energies biexciton binding energies of up to 5.0 meV are found, while in thin and more weakly confined QDs the electron wavefunction penetrates into the surrounding barriers causing reduced biexciton binding energies of less than 2.0 meV. This result can be understood in terms of theoretical calculations of biexcitonic complexes in QDs with finite potential barriers.

Transport study of an ultra-low density dual quantum dot

We report on transport results of an ultra-low density dual quantum dot. We observe that the conductance measured across one low density quantum dot is affected dramatically by the existence of the other low density quantum dot in close proximity. We have found turn on/off characteristics and a hysteresis in the conductance through one quantum dot when the other quantum dot is switched on by the gate bias. All these features are reproducible and have strong temperature dependences. Our observation probes a new low density regime of coupled zero dimensional systems and we interpret our data as due to an exchange interaction driven instability similar to what was observed in a coupled two dimensional system.